std::ranges::views::drop, std::ranges::drop_view

 

C++

Language

Standard Library Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Ranges library

Range access
begin cbegin end cend	rbegin crbegin rend crend	size ssize data cdata	empty
Range primitives
iterator_tsentinel_t	range_size_trange_difference_t	range_value_t	range_reference_trange_rvalue_reference_t
Dangling iterator handling
dangling	borrowed_iterator_t	borrowed_subrange_t
Range concepts
range borrowed_range sized_range	common_range view viewable_range	input_range output_range forward_range	bidirectional_range random_access_range contiguous_range
Views
view_interface	subrange
Semiregular wrapper
Factories
empty_viewviews::empty	single_viewviews::single	iota_viewviews::iota	views::counted
Adaptors
views::all_tviews::all join_viewviews::join take_viewviews::take basic_istream_viewistream_view	ref_view                                split_viewviews::split take_while_viewviews::take_while elements_viewviews::elements	common_viewviews::common transform_viewviews::transform drop_viewviews::drop keys_viewviews::keys	reverse_viewviews::reverse filter_viewviews::filter drop_while_viewviews::drop_while values_viewviews::values

 

std::ranges::drop_view

Member functions

drop_view::drop_view

drop_view::base

drop_view::begin

drop_view::end

drop_view::size

Deduction guides

 

template< ranges::view V > class drop_view : public ranges::view_interface<drop_view<V>>	(1)	(since C++20)
namespace views {     inline constexpr /*unspecified*/ drop = /*unspecified*/; }	(2)	(since C++20)

1) A range adaptor consisting of elements of the underlying sequence, skipping the first N elements.

2) The expression views::drop(E,F) is expression-equivalent to (where T is std::remove_cvref_t<decltype((E))> and D is ranges::range_difference_t<decltype((E))>):

• ((void)F, static_cast<T>(E)), if T is a ranges::empty_view;
• T{ranges::begin(E) + std::min<D>(ranges::size(E), F)}, ranges::end(E), if T models both random_access_range and sized_range, and T is a specialization of

• std::span where T::extent == std::dynamic_extent,
• std::basic_string_view,
• ranges::iota_view, or
• ranges::subrange;

• otherwise, drop_view{E, F}.

In all cases, decltype((F)) must model std::convertible_to<D>.

drop_view models the concepts contiguous_range, random_access_range, bidirectional_range, forward_range, input_range, common_range, and sized_range when the underlying view V models respective concepts.

Expression-equivalent

Expression e is expression-equivalent to expression f, if e and f have the same effects, either are both potentially-throwing or are both not potentially-throwing (i.e. noexcept(e) == noexcept(f)), and either are both constant subexpressions or are both not constant subexpressions.

Member functions

(constructor)	constructs a drop_view (public member function)
base	returns a copy of the underlying (adapted) view (public member function)
begin	returns an iterator to the beginning (public member function)
end	returns an iterator or a sentinel to the end (public member function)
size	returns the number of elements. Provided only if the underlying (adapted) range satisfies sized_range (public member function)

Example

Run this code

#include <ranges>
#include <vector>
#include <iostream>
 
int main()
{
    std::vector nums = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
 
    for (int i : nums | std::views::drop(2))
        std::cout << i << ' ';
    std::cout << '\n';
 
    for (int i : std::views::iota(1, 10) | std::views::drop(2))
        std::cout << i << ' ';
    std::cout << '\n';
 
    for (int i : std::ranges::drop_view{nums, 2})
        std::cout << i << ' ';
    std::cout << '\n';
}

Output:

3 4 5 6 7 8 9 
3 4 5 6 7 8 9 
3 4 5 6 7 8 9